Hey, thank you very much for the feedback!
I have a plan to redo the tutorial, the mage towers, and the UI and I have added your notes to my "redesign to-do list". The feedback you gave is very valuable and I can imagine that it took a lot of time to write it as well, I appreciate this a lot.
To answer the question of progress, there are more eras after modern era (Scifi, dystopian, and extinction era --> endless mode) that are unlocked when the game releases, on top of more resources (unlocks in that abandoned mine) and more units. The new resources will have more interesting upgrades instead of just "gather X times faster" (although there will be a few of those still). I do feel like your question was a rhetorical question though and you are telling me that the demo in its current state does not show this. I will think of a way to show the player that there is a lot more content past the demo.
I agree on the fact that the pace/style is a little bit over the place, for example it is serious and then all of the sudden it is not. I had no plan and no drawing board when starting out the project (big mistake), and I need to iron this out.
Thank you again for the lengthy feedback, I will try my best to improve this project as much as I can. The game releases in November but I should have time to implement most or all changes.